THE MINERALS OF IDAHO 



225 



a later filling of small vugs in it. A few grains of chalcopyrite are 

 inclosed in the quartz. Selected gray carbonate upon analysis gave 

 the following results and ratios: 



Dolomite, Monitor mine 

 [Earl V. Shannon, analyst] 



Constituent 



Percent 



Ratios 



Manganese carbonate (MnCO 3) _ I 0.45 



Iron carbonate (FeCO 3)-- 6.73 



Magnesium carbonate (MgCO 3) -J 28. 77 



Calcium carbonate (CaCO 3) | 64.05 



Total. ; 100.00 



0. 0040] 

 .059 1^0. 4126 

 . 3495] 

 . 6531 . 6531 



The ratio of Mn + Fe + Mg to Ca is 1 to 1.58 and the ratio of Fe + 

 Mn to Mgis 1 to 5.51. 



The fourth dolomite analyzed is from the Manhattan prospect, 1}4 

 miles northwest of the Monitor mine, which is located on a large vein 

 of quartz and carbonate in which no commercial ore has been found. 35 

 The specimen consists of a carbonate in cleavage rhombs up to 2 cm. 

 on an edge. The carbonate originally lined an open space subse- 

 quently filled with quartz, and although the original color of the 

 carbonate was probably gray it is now brown from dump weathering. 

 There are no ore minerals in the specimen. The carbonate, upon 

 analysis gave the results which, recalculated after deducting quartz, 

 are stated below. 



Dolomite, Manhattan prospect 

 [Earl V. Shannon, analyst] 



Constituent 



Percent 



Ratios 



Manganese carbonate (MnCO 3)-.- 

 Iron carbonate (FeCO 3) 



Magnesium carbonate (MgCO 3)-.. 

 Calcium (lime) carbonate (CaCO 3) 



Total 



0.24 

 10.79 

 28.23 

 60.74 



0. 00211 

 . 0948 M. 4399 

 . 3430j 

 . 6194 . 6194 



100.00 



The ratio of other bases to lime is 1 to 1.41 and that of iron plus 

 manganese to magnesia is 1 to 3.54. 



A large enough series of analyses of the carbonates from these 

 deposits would probably show a complete gradation from the fer- 

 riferous dolomites described above to the magnesian ankerites of the 

 following section. Out of six thus far analyzed, 4 are classifiable as 

 dolomite and 2 as ankerite; and a similar proportion of those not 

 analyzed may belong to each group. 



35 The prospects from which the above dolomites came have been described by F. C. Calkins and E. L. 

 Jones, jr., U. S. Oeol. Survey, Bull. 540, pp. 167-211, 1914. 



54317— 26t 16 



